1. Field of the Invention
The present invention relates to a method for producing a preform used for the manufacture of a metal matrix composite, and more particularly to a method for producing an SiC preform having a high volume fraction of 70% or more using SiC powder in accordance with a ball milling and pressing process.
2. Description of the Related Art
The remarkable technical development in the 1990""s in technical fields associated with electronic components has resulted in requirements for the materials of electronic packaging components to have specific characteristics as follows.
First, the material of an electronic packaging component should have a thermal expansion coefficient similar to that of a semiconductor chip encapsulated by that packaging component. By virtue of such a thermal expansion coefficient, it is possible to minimize thermal stress generated due to a thermal expansion coefficient difference between the semiconductor chip and the material of the electronic packaging component when heat is generated from the electronic packaging component. By virtue of such an electronic packaging component, an improvement in the life of semiconductor devices may be achieved.
Second, for an electronic packaging component, it is necessary to select a material capable of efficiently discharging heat generated from a semiconductor device using the electronic packaging component. Since semiconductor devices are sensitive to heat and impact, products using such semiconductor devices should be protected from impact. Such products should also have an ability to easily discharge heat.
Recently, electronic products have been developed toward a compact size so that they are conveniently portable. For such compact electronic products, accordingly, materials having characteristics of a low density have been preferably used. For such low-density materials, there may be metal matrix composites which have been recently highlighted for electronic packaging materials.
Metal matrix composites have characteristics of a high thermal conductivity and superior mechanical characteristics while exhibiting a relatively good workability because they use a metal matrix. Such metal matrix composites also has a low thermal expansion coefficient, as compared to other metal materials, because they use, as a reinforcement, ceramic having a low thermal expansion coefficient, thereby causing the thermal expansion of the metal matrix to be suppressed. Such metal matrix composites may also have designing characteristics capable of adjusting the thermal expansion coefficient thereof to a desired level. Such designing characteristics may be obtained by adjusting the volume fraction of the reinforcement. By virtue of such characteristics, metal matrix composites have been highlighted in association with applications to materials of electronic packaging components and materials of aerospace products, such as artificial satellites or spaceships, which should be strictly controlled in terms of a dimension variation resulting from a thermal expansion.
Such an increased interest in metal matrix composites has also resulted in an increased interest in reinforcement preforms used in the production of those metal matrix composites.
For a conventional preform production method, there may be a vacuum-assisted extraction method which is mainly used in the production of fiber preforms. This vacuum-assisted extraction method is a method of mechanically mixing a reinforcement with a binder in a stirrer, thereby forming a slurry, and extracting the slurry in vacuum, thereby producing a reinforcement preform. Such a particle reinforcement preform produced in accordance with such a vacuum-assisted extraction method has an average reinforcement volume fraction of about 50%. In order to use such a preform for the production of a metal matrix composite for electronic packaging components, however, the reinforcement volume fraction should be 70% or more. When the preform has a reinforcement volume fraction of 70% or more, it can have a thermal expansion coefficient of 6 to 7 ppm/K similar to those of semiconductor chips.
Therefore, an object of the invention is to provide a method for producing an SiC preform, which has a high volume fraction, and is capable of a reinforcement for metal matrix composites, using a ball milling and pressing process.
In accordance with the present invention, this object is accomplished by providing a method for producing an SiC preform having a high volume fraction, comprising the steps of: mixing SiC particles of different particle sizes each selected from a range of 0.2 to 48 xcexcm with an organic binder, an inorganic binder, an aggregating agent, and distilled water, thereby producing a mixture, and stirring the mixture in accordance with a ball milling process, thereby producing a slurry containing the SiC particles; pouring the slurry containing the SiC particles into a mold having upper and lower molds respectively provided with absorbent bodies, and squeezing the slurry in the mold, thereby reducing a residual moisture content of the slurry; completely drying the slurry reduced in residual moisture content, thereby producing an SiC preform; and calcinating the SiC preform.